Method and system for measuring three-dimensional displacement

Abstract: A method for measuring three-dimensional displacement of a mass comprises the steps of providing a measuring object placed on the end surface of the mass, for reflecting at least a fraction of three-dimensional displacement of the mass, arranging a displacement measuring equipment for free displacement relative to the mass and in opposition to the measuring object, and measuring three-dimensional relative displacement of the mass by detecting relative displacement of sad displacement indicative means relative to the displacement measuring equipment by the latter. The method is implemented by a three-dimensional displacement measuring system comprises a measuring object placed on the end surface of the mass, for reflecting at least a fraction of three-dimensional displacement of the mass, a displacement measuring equipment arranged for free displacement relative to the mass and in opposition to the measuring object, for measuring three-dimensional relative displacement of the mass by detecting relative displacement of sad displacement indicative means relative to the displacement measuring equipment by the latter. The method and system is suitable for measuring displacement of a rock across a crack.

Description: The present invention relates generally to a method and a system for measuring three-dimensional displacement of a mass. More specifically, the invention relates to a method and a system suitable for measuring three-dimensional displacement of a discontinuous surface, such as a crack in a rock or a natural joint and so forth. Conventionally, in fields of mechanical engineering, civil engineering and so forth, a non-contact type distance measuring equipment, such as a laser type displacement gauge, or a contact type displacement gauge employing a differential transformer and so forth are used practically. Namely, these measuring equipments performed high precision measurement of a displacement of a mass as an object for measurement (hereinafter referred to as measuring object) as a relative displacement from a reference portion where various displacement gauges are placed. Also, particularly in the field of civil engineering and mining, or in the field of geophysics, measurement of displacement of a foundation, such as a rock, is performed for appropriately evaluating behavior of rock or crust. As a method for measuring the displacement of the foundation, a measuring method employing an extensometer is typically employed. Namely, this method makes analysis of the displacement of the foundation by setting a fixed measuring point within a bore hole formed in the foundation, such as the rock, and measuring a variation of a distance between the fixed measuring point and a measuring point located at the opening end of the bore hole on the earth by means of the extensometer. However, when the displacement of the mass is measured by the conventional measuring system and method, the relative displacement from the reference portion where the displacement gauge is located is merely measured as a linear relative displacement. Therefore, in order to measure the three dimensional displacement of the mass, displacement measurements by means a plurality of measuring equipments which are arranged three-dimensionally. This makes installation of the measuring equipments and collection of measured data complicate. Furthermore, in particular, when three-dimensional behavior of the foundation is to be evaluated by the extensometer, since the measuring method employing the extensometer permits only evaluation of relative linear displacement between two measuring points along an axis of the bore hole, it is inherent to three-dimensionally arrange a plurality of bore holes to perform multi-axes and multi-point measurement for three-dimensional evaluation. In addition, in the method, it is not possible to instantly detect behavior discontinuous surface, such as crack of the rock, natural joint or so forth which sensitively reflects variation of stress condition of the foundation. Namely, in the conventional method employing the extensometer, a problem is encountered in requiring a huge amount of experiments for performing multi-axes and multi-points measurement for evaluating the three-dimensional behavior of the foundation. Also, the conventional method cannot make analysis of the behavior by specifying the discontinuous surface but rather unitarily evaluates deformation of the discontinuous surface associating with variation of the stress condition in the foundation and displacement of the foundation as a continuous body. Therefore, it is not possible to perform evaluation by specifying deformation of the discontinuous surface primarily determining deformation of the foundation. In the prior art, a further problem is encountered in impossibility of proper evaluation of relationship between the behavior of the overall foundation and the behavior of the discontinuous surface, deformation direction, deformation magnitude. GB-A-2109443 discloses a method for determining the position and location of a device for producing a connecting boring in the ground between two vertical bores. This cross borer device has a front cylindrical part and rear cylindrical part moving in alternation, the operation of determining the position and location being carried out by incrementally adding together the vectors of movement of the cross borer. An object of the present invention is to provide a three-dimensional displacement measuring system which can easily evaluate three-dimensional behaviour of foundation without requiring multi-axes and multi-point measurement and permits high precision and effective evaluation of deformation of the foundation by specifically measuring deformation of a discontinuous surface primarily determining most of deformation of the foundation. According to the present invention, there is provided a three-dimensional displacement measuring system for measuring relative displacement between a measuring object and a displacement measuring equipment, characterized in that: said measuring object includes a first cylindrical member and at least three surface members mounted on the end surface thereof, said surface members respectively oriented in mutually perpendicular directions, for representing at least a fraction of relative three-dimensional displacement therebetween; and said displacement measuring equipment includes a second cylindrical member and at least three displacement sensors arranged to contact with said three surface members respectively for directly detecting relative displacement of corresponding surface members, for measuring three-dimensional relative displacement of said measuring object and said displacement equipment by respectively detecting relative displacement of said surface members relative to said displacement sensors by the latter. The displacement measuring equipment may comprise at least one differential transformer displacement sensor contacting with the surface member. In one example, the differential transformer displacement sensor comprises measuring elements to be constantly maintained in contact with the surface members and a differential transformer portion connected to the measuring elements. The first and second cylindrical members may have fixing means press fitted onto the peripheral wall surface of the bore hole for fixing the first and second cylindrical members within the bore hole. The fixing means may comprise a fixing rod slidably extending radially through each of the cylindrical members. In the further preferred construction, the system may further comprise a guide means, on which the first and second cylindrical members are fixed by means of the fixing rod, and the first and second cylindrical members are guided in the bore hole in a position fixed on the guide means and restricted relative displacement to each other. Releasing and fixing of the cylindrical member is done by sliding the fixing rod. Other objects, features and advantages of the present invention will become clear from the detailed description given hereinafter with reference to the accompanying drawings. The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the present invention, which, however, should not be taken to be limitative to the invention, but are for explanation and understanding only. In the drawings: Fig. 1 is a section showing an embodiment of the three-dimensional displacement measuring system according to the present invention, adapted for measurement of displacement of a discontinuous surface of a rock; Fig. 2 is an enlarged view of a part of the three-dimensional displacement measuring system of Fig. 1 ; and Fig. 3 is a section showing one example of a differential transformer displacement gauge in the three-dimensional displacement measuring system OF Fig. 1 . The preferred embodiments of a three-dimensional displacement measuring system and method will be discussed hereinafter in detail with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instance, well-known structures are not shown in detail in order to unnecessary obscure the present invention. An embodiment of the three-dimensional displacement measuring system according to the invention will be discussed with reference to Figs. 1 to 3 . The three-dimensional displacement measuring system 60 illustrated in these figures is designed for measuring displacement of the crack in the rock as one example of the discontinuous surface. The three-dimensional displacement measuring system 60 generally comprises a measuring object 61 disposed in the bore hole 33 formed in the rock across the crack 32 and located in the rock 31a positioned at one side of the crack 32, a displacement measuring equipment 62 located within the rock 31b at the other side of the crack and following to the measuring object 61, and a fixing guide member 63 detachably attached to the measuring object 61 and the displacement measuring equipment 62. As shown in enlarged section of Fig. 2, the measuring object 61 has a first cylindrical portion 64 having a tip end with a smaller diameter. On the read end surface of the first cylindrical member 64, a surface member 65a is mounted with orienting the surface in parallel to the rear end surface of the first cylindrical member. Another pair of surface members 65b (only one is shown) are oriented perpendicularly to the surface member 65a and extending rearwardly. The pair of surface members 65b also intersects perpendicularly to each other. The first cylindrical member 64 carries a fixing rod 66. The fixing rod 66 has an expanding and contracting device constructed with a combination of a hydraulic cylinder and a spring. The expanding and contracting device is connected to a pressure line 67 to receive a hydraulic pressure controllably supplied from a working base at the opening end of the bore hole 63 on the earth. The expanding and contracting device is responsive to the hydraulic pressure supplied through the pressure line 67 to drive a fixing pin 68 and a hole wall abutment 69 provided at both axial ends of the fixing rod 66 to cooperatively extend from or contract into the fixing rod. Namely, in the action, when the fixing pin 68 is driven toward left to protruded by application of the hydraulic pressure, the hole wall abutment 69 is driven to be retracted. On the other hand, by releasing the hydraulic pressure, the fixing pin 68 is retracted and the hole wall abutment 69 is projected. On the other hand, the displacement measuring equipment 62 has a second cylindrical member 70 following the first cylindrical member 64. On the tip end surface (the surface opposing to the read end surface of the first cylindrical member 64 where the three surfaces 65, i.e. surface members 65a and 65b, a support base 71 is rigidly secured. On the support base 71, three differential transformer displacement sensor (hereinafter referred to as "LVDT displacement sensor) 72 are mounted. Each LVDT displacement sensor 72 is arranged to perpendicularly mate with corresponding one of the three surfaces of the surface members 65a and 65b. The second cylindrical member 70 also includes the fixing rod 66 having the identical construction to that provided in the first cylindrical member 64. At a gap between the first and second cylindrical members 64 and 70, a membrane wall 74 serving as a water-tight seal is mounted with covering the three surface members 65 and the LVDT displacement sensor 72 for protruding the latter. On the external surface of the first and second cylindrical members 64 and 70, a plurality of supporting legs 74 are arranged with a given interval in the circumferential direction at both circumferential sides of the fixing pins 68 of the fixing rods 66. These supporting legs 74 are cooperative with the hole wall abutments 69 of the fixing rod 66 when the hole wall abutments 69 are projected from the fixing rod to abut against the hole wall, so as to fix the first and second cylindrical members 64 and 70 at respectively predetermined positions within the bore hole 33. The LVDT displacement sensor 72 is per se known in the art. For example, the LVDT displacement sensor 72 comprises a primary coil 76, a secondary coil 77, a differential transformer portion 75 including a core 78 formed of a magnetic body and disposed at the center of the primary and secondary coils, a measuring element 79, a spindle 80, a measuring pressure spring 81 and so forth. The measuring element 79 is held in contact with the surface members 65a and 65b of the three surfaces 65 and adapted to be shifted in axial direction according to displacement of the corresponding surface member. The magnitude of shifting of the measuring element 79 is detected by exciting the primary side of the differential transformer portion 75 by an alternating current, generating a secondary signal proportional to the shifting magnitude of the measuring element 79 which is directly connected to the core 78 via the spindle 80, detecting the secondary signal to output as a direct current signal indicative of the shifting magnitude of the measuring element 79, and in turn indicative of the displacement of the three surfaces 65. The fixing guide member 63 comprises a thin plate member 82 curved along the external surfaces of the first and second cylindrical members 64 and 70. The circumferential width of the plate member 82 is determined so that it may be placed between the support legs 74. For the plate member 82, engaging holes 83 for engaging with the fixing pins 68 of the d¥fixing rods 66 are formed. Therefore, by projecting the fixing pins 68 to engage with the engaging holes 83, the measuring object 61 including the first cylindrical member 64 and the displacement measuring equipment 62 including the second cylindrical member 70 are fixed on the fixing guide member 63. At this condition, the measuring object 61 and the displacement measuring equipment 62 are fixedly connected to each other and thus prevented from relative displacement. The support leg 74 maintains a clearance between the peripheral wall surface of the bore hole 33 and the external peripheries of the cylindrical members 64 and 70 for protecting the fixing guide member 83 and facilitate withdrawal of the fixing guide member 63. As shown in Fig. 1 , as a supporting carriage is provided in the fixing guide member 63, a wheeled centrizer 84 is provided. The plate member 82 set forth above is extended frontwardly from the wheeled centrizer 84. To the wheeled centrizer 84, an extension rod 85 reaching the opening end of the bore hole is connected. Also, the wheeled centerizer 84 carries a bore hole television camera 86 for visually monitoring the wall surface of the bore hole 33. It should be noted that the LVDT sensor 72 of the displacement measuring equipment 62 is connected to an amplifier of the LVDT displacement sensor, an A/D converter, a CPU for performing measuring control and data file management, a data memory and so forth via various connection lines. For measuring the displacement of the crack 32 in the rock employing the three-dimensional displacement measuring system 60 as set forth above, the three-dimensional displacement measuring system 60 is disposed within the bore hole 33 across the crack 32. The installation of the three-dimensional displacement measuring system is performed through the following process. The measuring object 61 and the displacement measuring equipment 62 are inserted into the bore hole 33 in a condition fixed to each other by the fixing guide member 63. By connecting extension rods 85, the assembly of the measuring object 61 and the displacement measuring equipment 62 are pushed to the predetermined positions in the bore hole 33 with sliding of the fixing guide member 63. Since the fixing guide member 63 includes the wheeled centrizer 84, the assembly of the measuring object 61 and the displacement measuring equipment 62 with the fixing guide member 63 can be smoothly moved within the bore hole 33. During movement of the assembly of the measuring object 61 and the displacement measuring equipment 62, the bore hole television camera 86 picks up the image of the peripheral wall of the bore hole 33 for visual display, the accurate position of the crack 32 can be detected. One the accurate position of the crack 32 is detected by means of the bore hole television camera 86, the fixing guide member 63 is pulled back for a predetermined stroke. Then, the positions of the measuring object 61 within the rock 31a at one side of the crack 32 and the displacement measuring equipment 62 within the rock 31b at the other side of the crack 32 are adjusted to place them at respectively predetermined positions. Thereafter, the hydraulic pressure applied to the expanding and contracting device of the fixing rod 66 is drained so that the spring therein overcomes the hydraulic force to retract the fixing pins 68 away from the engaging holes 83, and at the same time, to protrude the hole wall abutment 69 to establish pressure contact thereon. Accordingly, the engagement between the fixing pins 68 and the engaging holes 83 is released to place the measuring object 61 and the displacement measuring equipment 62 free from fixing guide member 63. Simultaneously, abutment of the hole wall abutment onto the peripheral wall surface of the bore hole 33 in cooperation with the supporting legs 74 causes the measuring object 61 and the displacement measuring equipment 62 rigidly fixed at respectively predetermined positions in the bore hole 33. By this installation of the three-dimensional displacement measuring system 60 is completed. Attention should be attracted to the fact that the measuring object 61 and the displacement measuring equipment 62 are held in the fixed position on the fixing guide member 63 until the three-dimensional displacement measuring system 60 is set in the bore hole 33. In this manner, the relative position between the measuring object 61 and the displacement measuring equipment 62 are maintained at fixed condition. By this, narrowing of the measuring range, offsetting out of measuring range and error in measurement of the LVDT displacement sensor 72 due to offset of the initial fixing position can be successfully avoided, The fixing guide member 63 which is released from the measuring object 61 and the displacement measuring equipment 62 as fixing of the latter in the bore hole 33 is removed together with the bore hole television camera 86 via the extension rod 85. When the rock 31a displaces relative to the rock 31b mating across the crack 32, the measuring object 61 also displaces relative to the displacement measuring equipment 62. This relative displacement appears as displacement of any one or more of the three surfaces 65 of the surface members 65a and 65b to cause shifting of the corresponding measuring element or elements 79. Thus, by monitoring displacement of the three surfaces 65 by three LVDT displacement sensors 72, the relative displacement of the foundation positioned across the crack 32 can be monitored with high precision. As set forth above, the LVDT displacement sensors 72 of the displacement measuring equipment 62 are connected to the amplifiers of the LVDT displacement sensors 72, the A/D converter, the CPU performing measurement control and data file management, the data recording memory and so forth. Therefore, the behavior of the crack can be monitored automatically for a long period. It should be noted that when a predetermined period is elapsed and measurement is completed, the hole wall abutments 69 are released from engagement with the peripheral wall of the bore hole. Then, the three-dimensional displacement measuring system 60 can be recovered from the bore hole via the pressure line 67. Here, when step is formed in the bore hole 33 due to deformation of the rocks, the displacement measuring equipment 62 may be separated from the measuring object 61 so that it may solely recovered. It should be noted that although the shown embodiment employs three mutually perpendicularly intersecting surfaces for monitoring three-dimensional behavior of the crack 32, it is naturally possible to employ more surfaces for measuring displacement. Although the invention has been illustrated and described with respect to exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without departing from the scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodied within the scope set out in the appended claims.

Claims: A three-dimensional displacement measuring system (60) for measuring relative displacement between a measuring object (61) and a displacement measuring equipment (62), characterized in that : said measuring object (61) includes a first cylindrical member (64) and at least three surface members (65) mounted on the end surface thereof, said surface members (65) respectively oriented in mutually perpendicular directions, for representing at least a fraction of relative three-dimensional displacement therebetween; and said displacement measuring equipment (62) includes a second cylindrical member (70) and at least three displacement sensors (72) arranged to contact with said three surface members (65) respectively for directly detecting relative displacement of corresponding surface members (65), for measuring three-dimensional relative displacement of said measuring object (61) and said displacement equipment (62) by respectively detecting relative displacement of said surface members (65) relative to said displacement sensors (72) by the latter. A system as set forth in claim 1, wherein a water-tight seal member (74) is mounted between said first cylindrical member (64) and said second cylindrical member (70). A system as set forth in claim 1, wherein said displacement measuring sensor is a differential transformer displacement sensor (72). A system as set forth in claim 3, wherein said differential transformer displacement sensor (72) comprises a measuring element (79) to be constantly maintained in contact with said surface members (65) and a differential transformer portion (75) connected to said measuring element (79). A system as set forth in any preceding claim, wherein said first and second cylindrical members (64, 70) have fixing means for fixing said first and second cylindrical members (64, 70) against a surrounding peripheral surface. A system as set forth in claim 5, wherein said fixing means comprises a fixing rod (66) slidably extending radially through each of said cylindrical members (64, 70). A system as set forth in claim 6, wherein said fixing rod (66) operates by hydraulic force. A system as set forth in claim 7, further comprising a guide means, on which said first and second cylindrical members (64, 70) are fixed by means of said fixing rod (66), and said first and second cylindrical members are guided in a position fixed on said guide means and restricted in relative displacement to each other. A system as set forth in claim 8, wherein said guide means comprises a plate member (82) having an engaging hole (83), and said cylindrical members (64, 70) are fixed on said plate member (82) by engaging of ends of said fixing rods (66) into said engaging holes (83). A system as set forth in claim 9, wherein said fixing rod can be slid by control of the hydraulic force to release engagement between said fixing rods (66) and said engaging holes (83), to hold said first and second cylindrical members (64, 70) in predetermined positions. A system as set forth in claim 10, wherein said fixing rod (66) is slidable to a position of released engagement of one end thereof with said engaging hole (83), and wherein in this position the other end thereof projects for press fitting on the surrounding peripheral surface. A system as set forth in claim 5, wherein said fixing means further comprises supporting legs (74) provided on external surfaces of said first and second cylindrical members (64, 70), said supporting legs being cooperative with said fixing rod (66) for fixing said cylindrical member (64, 70) against the surrounding peripheral surface. A system as set forth in claim 8, wherein said guide means includes a monitoring means for monitoring the surrounding peripheral surface. A system as set forth in claim 13, wherein said monitoring means comprises a television (86) for picking up the image of the surrounding peripheral surface for visual display. A system as set forth in claim 8, wherein said guide means comprises a wheeled centrizer (84). A system as set forth in claim 9, wherein said guide means further comprises an extension rod (85) connected to said plate member (82).

Inventors: KOSUGI MASAYUKI, TAMAI AKIO, KOSUGI, MASAYUKI, TAMAI, AKIO
Applicants: AGENCY IND SCIENCE TECHN, OHBAYASHI CORP, AGENCY OF INDUSTRIAL SCIENCE AND TECHNOLOGY, OBAYASHI CORPORATION
Application year: 1994
Main classification: G01B7
IPC codes: E21B49, G01B11, G01B5, E21B47